This works like the LttP randomizer, in that it generates a ROM file with randomized item locations. You can choose between Casual, Speedrunner and Masochist modes, which I assume affects how difficult some of the item locations are. (ie: varia suit in lower norfair or something)

Maybe not. I got stuck on my first run on Casual, because of no Morph Ball or Missiles. Screw Attack and Space Jump let me access a Power Bomb, but without Morph Ball I could not use it. Maybe I'll double check after I get through this current second run.
edit: I figured it out

Completable seed: C0949919

edit: sorry, I was wrong, this is how difficulties work:

This is a fundamental shift in the way difficulties work. Instead of having "Easy", "Normal", and "Hard", the difficulties are now "Casual", "Speedrunner", and "Masochist." If you aren't a speedrunner, don't pick "Speedrunner." If you aren't a masochist, don't pick "Masochist." Easy as that.

A major overhaul of the randomization for all difficulties has taken place.

Among the changes, now Missile and Super Missile are possible first items in Speedrunner and higher difficulties.

Casual difficulty has the 100 normal items hidden from vanilla Super Metroid. A great intro for those who want to play something a little more random, but nothing tricky.

Also, no items will be hidden in the scenery on Casual except those normally hidden in vanilla Super Metroid.

So I think speedrunner/masochist removes some spawns to make things harder.

I still haven't checked this out, but there have been a few streams of Super Metroid randomized on Vinesauce recently that reminded me about this and re-piqued my interest in it. I think I'll give it a go sometime this week.

DUDE. I love SM Randomizer, it's great. I actually especially love when the first item is Screw Attack or Speed Booster and not Morph Ball because of how interesting and different it makes the early game.

Just beat a run on "speedrunner difficulty" for the first time in a while. I had to use bombjumps, tricky walljumps (but not CWJ), mockball, spore spawn skip, lower Norfair lava gravity jump, and zebetite skip, the last two of which I had to learn for the run (I had no other way to get into Lower Norfair without space jump!) Clear time was 2:49 IGT.

If we ever get around to doing this competitively, casual is definitely best, because that was too tricky for a race.

Also, the thing is, on casual and speedrunner difficulty at least, each important key item (like Varia/Gravity, Charge Beam, Speed Booster, etc) shows up in multiple locations, so you can get it in any of those places, but if you got it already, it'll just be replaced with missiles (or in speedrunner, will be empty). Also, protip: you may have to shoot item balls to reveal them; some will be invisible until being shot even if they'd be normally visible.

You should try it. It's not so bad and can sometimes be easier than normal, like if you get screw attack as one of the first items.